The present invention relates to an actuator with clutch mechanism, more particularly, to an actuator that is used in a power-assisted vehicle door and in a drum rotating mechanism of a photocopier.
Some vehicles have power-assisted doors with actuators. The actuator applies assisting force to a vehicle door when a user opens or closes the door. For example, Japanese Laid-Open Patent Publication No. 6-328940 discloses such a power-assisted door. The apparatus of the publication includes an actuator located in the panel of a door. The actuator has an electric motor as a drive source. The motor has a gear fixed to the rotary shaft. The gear is coupled to a worm gear via a reduction gear. The worm gear is coupled to a slider. The slider is coupled to the vehicle body with an assisting force applying member and brackets. Rotation of the motor is converted into reciprocation of the slider by the worm gear. The reciprocation of the slider is, in turn, converted into opening and closing motion of the door. When predetermined conditions are satisfied, for example, when an operation switch is turned on, the force of the actuator (assisting force) permits the door to be opened or closed with a small force applied by the user.
The number of gears and the lead angle of the worm gear are determined such that the rotary shaft of the motor is rotated by force applied by the door. Therefore, when the predetermined conditions are not satisfied, or when the actuator is not working, the door can be opened and closed manually. However, when the door is opened or closed manually, the worm gear is rotated by the force applied from the door. In other words, the force is applied to the output side of the apparatus. Thus, a great force is required for opening and closing the door manually.
An electromagnetic clutch may be used for transmitting rotational force from the worm gear (driving member) to the gear of the door (driven member) and for prohibiting the worm gear from receiving rotational force from the gear of the door. If the electromagnetic clutch does not transmit rotational force from the gear of the door to the worm gear when the door is opened or closed manually, the worm gear does not receive any load. This permits the door to be opened and closed with a small force. However, the electromagnetic clutch increases the size of the apparatus and increases the cost.
Accordingly, it is an objective of the present invention to provide a clutch mechanism, an actuator with clutch mechanism, and a power-assisted door using the actuator that mechanically transmit force from a driving member to a driven member, permits the driven member to rotate without applying load to the driving member, and reduces the size and the costs.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a clutch mechanism is provided between a driving rotor and a driven rotor. The clutch mechanism selects from a state for transmitting rotational force of the driving rotor to the driven rotor and a state for discontinuing the transmission of rotational force generated from the driven rotor to the driving rotor. The clutch mechanism includes a plurality of rolling bodies and a holder. The rolling bodies are located between the driving rotor and the driven rotor. The holder holds the rolling bodies and permits the rolling bodies to roll. The holder supports the rolling bodies such that the rolling bodies are switched between a transmitting position and a disconnecting position. When held at the transmitting position, the rolling bodies are engaged with both of the driving rotor and the driven rotor so that rotational force of the driving rotor is transmitted to the driven rotor. When held at the disconnecting position, the rolling bodies are disengaged from the driving rotor so that the transmission of rotational force from the driving rotor to the driven rotor is discontinued. When external rotational force is applied to the driven rotor, the holder sets the rolling bodies to the disconnecting position.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.